JP2571629B2 - Failure diagnosis device for variable valve timing control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnosis device that performs a self-diagnosis of a failure of a variable valve timing control device of an internal combustion engine.

2. Description of the Related Art Since intake and exhaust valves of an internal combustion engine are driven to open and close by a camshaft that rotates in synchronization with a crankshaft, the opening and closing timing, that is, the valve timing, is usually fixed. In order to optimize the valve timing according to the operating conditions, various variable valve timing control devices capable of variably controlling the valve timing have been conventionally proposed. For example, Japanese Patent Application Laid-Open No. 55-96311 discloses that a timing belt and a cam pulley or a cam sprocket around which a cam chain is wound are rotatably mounted on a camshaft and both are fixed by a hydraulic actuator using a helical gear or the like. There is disclosed a variable valve timing mechanism in which the phase with respect to the crank angle of the camshaft can be changed in two ways by relative rotation by an accuracy. Here, the supply of hydraulic pressure to the hydraulic actuator is controlled ON / OFF by an electromagnetic valve, and the valve timing is switched accordingly. In general, a control signal from a control unit based on the engine speed and load is used. , The switching is performed.

FIG. 5 (a) shows, by way of example, a valve lift characteristic when a variable valve timing mechanism is provided only on the intake valve side, and can be switched between the characteristic indicated by the solid line A and the characteristic indicated by the broken line B. .

Problems to be Solved by the Invention When the above-described variable valve timing control device fails due to some cause, for example, a defect in the control unit itself, a stuck electromagnetic valve, a broken wire in a harness, etc., a method of self-diagnosing the failure has conventionally been used. Absent. Therefore, although a malfunction such as a decrease in output may occur due to an irregular valve timing, the driver may not be able to notice and may continue to operate for a long period of time.

Means for Solving the Problems A failure diagnosis device for a variable valve timing control device according to the present invention includes an internal combustion engine having a variable valve timing mechanism capable of changing valve timing stepwise to a plurality of characteristics based on a control signal. In FIG. 1, as shown in FIG. 1, one or a plurality of vibration detection sensors 1 mounted at appropriate positions of an internal combustion engine and a plurality of seating times obtained by the variable valve timing mechanism are set correspondingly. Integrating means for integrating the output signals of the vibration detection sensor 1 for the plurality of integration periods obtained, and a seating time for determining the actual seating time within which period by comparing the integrated values of the respective integration periods. The discriminating means 3 collates the actual seating timing with the control condition of the variable valve timing mechanism, and determines whether the valve timing matches the control condition. Abnormality detecting means 4 for judging whether or not the characteristic is controlled to a corresponding predetermined characteristic.

Operation When an intake valve or an exhaust valve of an internal combustion engine is seated, mechanical vibration is generated in a cylinder head or a cylinder block by an impact at that time. This vibration is detected by the vibration detection sensor 1 and converted into an electric signal. Then, the output signal of the vibration detection sensor 1 is integrated for a plurality of integration periods corresponding to a plurality of seating times set in the variable valve timing control device. Here, during the period in which the sitting vibration is actually occurring, the integral value becomes large,
The integrated value during the period in which no sitting vibration occurs is small. Therefore, by comparing the magnitudes of the respective integral values, it is possible to determine in which period the actual seating time is.

Then, since the seating time during normal operation is determined from the control conditions of the variable valve timing mechanism, for example, the engine speed, the load, and the like, the presence or absence of an abnormality can be determined by the coincidence or inconsistency of this with the actual seating time.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a configuration explanatory view showing the configuration of one embodiment of the failure diagnosis device according to the present invention. For example, a crankshaft 12 and a camshaft 13 are provided on the intake side of an internal combustion engine 11 having a DOHC type valve mechanism. With a predetermined amount (eg, crank angle
A variable valve timing mechanism 14 is provided which can be changed by about 20 °. Although not shown in detail, the variable valve timing mechanism 14 includes a camshaft 13
And a solenoid valve that controls the introduction of hydraulic pressure to the actuator ON and OFF based on a control signal from a control unit 15 using a digital microcomputer. The valve timing is switched in two ways as indicated by the solid line A and the broken line B in FIG. 5 (a).

Further, a vibration detection sensor 16 is mounted at an appropriate position of the internal combustion engine 11, for example, at a side surface of the cylinder block. The vibration detection sensor 16 has the same configuration as a known knocking sensor using, for example, a piezoelectric element, and detects mechanical vibration of a cylinder block accompanying seating of an intake valve.
Since the vibration associated with the seating of the valve and the knocking vibration are in relatively close frequency ranges, it is possible to detect the seating vibration and the knocking vibration with one sensor.

The output signal of the vibration detection sensor 16 is input to the control unit 15.

Reference numeral 17 denotes a crank angle sensor that detects the rotation of the crankshaft 12 of the internal combustion engine 11. The crank angle sensor 17 includes a POS signal composed of a pulse signal for each crank angle of 1 ° indicating the rotation angle, and A REF signal for detecting the top dead center position of the cylinder is output. Reference numeral 18 denotes, for example, a hot-wire type air flow meter for detecting an intake air amount of the internal combustion engine 11, and reference numeral 19 denotes a water temperature sensor for detecting an engine cooling water temperature.

The control unit 15 performs control of the variable valve timing mechanism 14 and self-diagnosis of a failure thereof in accordance with a predetermined program, and further performs ignition timing control of an unillustrated spark plug, air-fuel ratio control, and the like, and is shown in FIG. As described above, the band-pass filter 21 that separates and passes only specific components specific to the sitting vibration and the knocking vibration from the output signal of the vibration detection sensor 16, and integrates the output signal of the band-pass filter 21 for a predetermined period after rectification. An integration circuit 22, an integration period signal generation circuit 23 for defining an integration period in the integration circuit 22, and an A / D conversion circuit 24 for A / D converting the output of the integration circuit 22 are provided. 25 is I / O port, 26 is CPU, 27
Indicates ROM and 28 indicates RAM. The integration period is set in units of the engine crank angle, and an integration period signal is output based on the POS signal and the REF signal from the crank angle sensor 17.

 Next, the operation of the above configuration will be described.

First, the switching of the variable valve timing mechanism 14 is controlled based on the rotation speed N during the internal combustion period and the basic fuel injection amount Tp. The rotation speed N is obtained based on the output signal of the crank angle sensor 17. The basic fuel injection amount Tp corresponds to the engine load, and is calculated from the intake air amount and the engine speed. FIG. 4 shows an OFF region (having the characteristics of the solid line A) and an ON region (having the characteristics of the broken line B) of the solenoid valve. The solenoid valve is turned ON only in the high load area where the injection amount Tp is Tp1 or more,
The valve timing is advanced as indicated by the broken line B. However,
When the cooling water temperature TW is equal to or lower than the predetermined temperature TW1, this control is not performed, that is, the state of the electromagnetic valve OFF is maintained regardless of the operation range.

On the other hand, in the vibration detection sensor 16, the seating vibration of the intake valve whose valve timing is variably controlled as described above, the seating vibration of the exhaust valve generated at a fixed timing, and the knocking vibration are shown in FIG. Detected as shown. This shows a case where the valve timing of the intake valve is in the state indicated by the solid line A as an example. Then, an integration period is given to the detection signal of the vibration detection sensor 16 as shown in FIG. Here, the period L1 is set corresponding to the seating timing of the valve timing indicated by the broken line B, and the period L2 is set corresponding to the seating timing of the valve timing indicated by the solid line A. Note that the period L3 is an integration period set in accordance with knocking occurrence timing in order to separate knocking vibration.

FIG. 5 (d) shows the output waveform output from the integrating circuit 22 in each of the above periods, and FIG. 5 (e) shows the A / D conversion value thereof. The integrated value S2 of the period L2 including the actual sitting time is larger than the integrated value S1 of the other period L1. Of course, if the valve timing of the intake valve is in the state indicated by the broken line B, the integrated value S1 is larger than the integrated value S2. Therefore, from the comparison between the two,
It is possible to reliably determine which of the characteristics (a) and (b) the actual valve timing has.

FIG. 6 shows an outline of a self-diagnosis program executed in the control unit 15. First, the engine speed N, the basic fuel injection amount Tp, and the coolant temperature TW are read (step 1), and then these are read. Is determined to be within the diagnostic conditions (step 2). That is, the engine speed N
Is diagnosed only when three conditions of N1 ≧ N ≧ N2, basic fuel injection amount Tp is Tp ≧ Tp1, and water temperature TW is TW ≧ TW1 are satisfied at the same time. Under this condition, the solenoid valve of the variable valve timing mechanism 14 is controlled to be ON as described above, and if the system is normal, the valve timing becomes as indicated by the broken line B.

If the rotational speed N or the like is within the above-described diagnostic conditions, the routine proceeds to step 3, where the integral values S1, S2 of the above-described integrating engines L1, L2
Is read, and in step 4, the magnitudes of the two are compared.
Here, if S1> S2, it means that the actual valve timing has the characteristic indicated by the broken line B in accordance with the control condition.
Is determined to be normal including the control system.

On the other hand, if S1 <S2, it means that the actual valve timing has the characteristic indicated by the solid line A contrary to the control condition, so the process proceeds to Steps 6 and 7 to determine "abnormal" Then, an appropriate warning is given by turning on a warning light.

In the above embodiment, the diagnosis is made as to whether the valve timing indicated by the broken line B is within the region where the solenoid valve is to be turned ON. It may be determined whether or not the timing has come.

EFFECT OF THE INVENTION As is clear from the above description, according to the failure diagnosis device for the variable valve timing control device according to the present invention, the actual seating timing of the intake valve or the exhaust valve whose valve timing is variably controlled is determined by the seating vibration. The variable valve timing control device operates normally, including mechanical failures and control unit abnormalities, based on the detection of abnormal conditions and control conditions of the variable valve timing mechanism. Can be reliably diagnosed. Further, the vibration detection sensor has an advantage that a normal knocking sensor can be used as it is and can be realized without any substantial increase in the number of parts.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing the configuration of the present invention, FIG. 2 is an explanatory diagram showing the configuration of an embodiment of the present invention, FIG. 3 is a block diagram showing a main part of a control unit, and FIG. FIG. 5 is a characteristic chart showing ON / OFF regions of the timing mechanism, FIG. 5 is a time chart showing a comparison between valve timing and each signal waveform, and FIG. 6 is a flowchart showing an outline of a self-diagnosis program. 1 ... Vibration detection sensor, 2 ... Integrating means, 3 ... Seating timing discriminating means, 4 ... Abnormality detecting means.

Claims (1)

(57) [Claims] An internal combustion engine provided with a variable valve timing mechanism capable of changing a valve timing to a plurality of characteristics in a stepwise manner based on a control signal. A vibration detection sensor, integrating means for integrating output signals of the vibration detection sensor for a plurality of integration periods set respectively corresponding to a plurality of seating times obtained by the variable valve timing mechanism, and integration of each integration period The seating timing determining means for comparing the values to determine which period the actual seating timing is in, and comparing the actual seating timing with the control condition of the variable valve timing mechanism to determine whether the valve timing is Variable valve timing control comprising: abnormality detection means for determining whether or not control is performed to predetermined characteristics corresponding to the above control conditions. Location of the fault diagnosis system.